chapter 13 wired lans: ethernet copyright © the mcgraw-hill companies, inc. permission required for...
TRANSCRIPT
Chapter 13
Wired LANs:Ethernet
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Chapter 5: Outline
13.1 13.1 ETHERNET PROTOCOLETHERNET PROTOCOL
13.2 13.2 STANDARD ETHERNETSTANDARD ETHERNET
13.3 13.3 FAST ETHERNETFAST ETHERNET
13.4 13.4 GIGABIT ETHERNETGIGABIT ETHERNET
13.5 13.5 10 GIGABIT ETHERNET10 GIGABIT ETHERNET
13.3
13-1 ETHERNET PROTOCOL13-1 ETHERNET PROTOCOL
The data-link layer and the physical layer are the territory of the local and wide area networks.
13.4
13.13.1 IEEE Project 80213.13.1 IEEE Project 802
In 1985, the Computer Society of the IEEE started a project, called Project 802, to set standards to enable intercommunication among equipment from a variety of manufacturers.
13.5
13.13.1 IEEE Project 80213.13.1 IEEE Project 802
Project 802 is a way of specifying functions of the physical layer and the data-link layer of major LAN protocols.
13.6
Figure 13.1: IEEE standard for LANs
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13.13.2 Ethernet Evolution13.13.2 Ethernet Evolution
The Ethernet LAN was developed in the 1970s by Robert Metcalfe and David Boggs.
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13.13.2 Ethernet Evolution13.13.2 Ethernet Evolution
Ethernet has gone through four generations:
●Standard Ethernet (10 Mbps), ●Fast Ethernet (100 Mbps), ●Gigabit Ethernet (1 Gbps), and ●10 Gigabit Ethernet (10 Gbps),
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Figure 13.2 : Ethernet evolution
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13-2 STANDARD ETHERNET13-2 STANDARD ETHERNET
We refer to the original Ethernet technology with the data rate of 10 Mbps as the Standard Ethernet.
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13.2.1 Characteristics13.2.1 Characteristics
Characteristics of the Standard Ethernet.
1. 10Mbps2.CSMA/CD3.UTP or Coax4.Min frame size is 512 bits (64 bytes)5.Max frame size is 12144 bits (1518 bytes)6.2500 meter distance between the furthest stations.
13.12
Figure 13.3: Ethernet frame
Data transmission.
Bytes are from left to rightThe bits in each byte are right to left.
Show how the address 47:20:1B:2E:08:EE is sent out online.
Example 13.1
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Show how the address 47:20:1B:2E:08:EE is sent out online.Solution
Example 13.1
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13.2.2 Addressing13.2.2 Addressing
Each station on an Ethernet network (such as a PC, workstation, or printer) has its own network interface card (NIC).
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13.2.2 Addressing13.2.2 Addressing
The NIC fits inside the station and provides the station with a link-layer address.
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13.2.2 Addressing13.2.2 Addressing
The Ethernet address is 6 bytes (48 bits), normally written in hexadecimal notation, with a colon between the bytes.
For example, the following shows an Ethernet MAC address:
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Figure 13.4: Unicast and multicast addresses
Define the type of the following destination addresses:
a.4A:30:10:21:10:1Ab.47:20:1B:2E:08:EEc.FF:FF:FF:FF:FF:FF
Example 13.2
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Define the type of the following destination addresses:a.4A:30:10:21:10:1Ab.47:20:1B:2E:08:EEc.FF:FF:FF:FF:FF:FF
Example 13.2
SolutionTo find the type of the address, we need to look at the second hexadecimal digit from the left. If it is even, the address is unicast. If it is odd, the address is multicast. If all digits are Fs, the address is broadcast. Therefore, we have the following:
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Example 13.2 (continued)
a. This is a unicast address because A in binary is 1010 (even).b. This is a multicast address because 7 in binary is 0111 (odd).c. This is a broadcast address because all digits are Fs in hexadecimal.
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13.22
Figure 13.5: Implementation of standard Ethernet
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Figure 13.5: Implementation of standard Ethernet
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13.2.3 Access Method13.2.3 Access Method
Standard Ethernet protocol is a broadcast network, needing an access method for the shared medium.
The standard Ethernet chose CSMA/CD with 1-persistent method.
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13.2.4 Efficiency of Standard Ethernet13.2.4 Efficiency of Standard Ethernet
The practical efficiency of standard Ethernet has been measured to be
The variable “a” is the ration of Propagation delay to transmission delay (a unit-less value).
Example 13.3
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What is the worse case efficiency for standard ethernet?
Assume the smallest frame size, and longest distance between stations (2500m).
Example 13.3
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What is the efficiency for a 100m maximum link separation?
Example 13.3
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13.29
13.2.5 Implementation13.2.5 Implementation
The Standard Ethernet defined several implementations, but only four of them became popular during the 1980s.
Table 13.1: Summary of Standard Ethernet implementations
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Figure 13.6: Encoding in a Standard Ethernet
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Figure 13.7: 10Base5 implementation
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Figure 13.8: 10Base2 implementation
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Figure 13.9: 10Base-T implementation
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Figure 13.10: 10Base-F implementation
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13.2.6 Changes in the Standard13.2.6 Changes in the Standard
Ethernet evolves to become compatible with other high-data-rate LANs.
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Figure 13.11: Sharing bandwidth
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Figure 13.12: A network with and without bridging
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Figure 13.13: Collision domains
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Figure 13.14: Switched Ethernet
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Figure 13.15: Full – duplex switched Ethernet
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13-3 FAST ETHERNET13-3 FAST ETHERNET
In the 1990s, Ethernet made a big jump by increasing the transmission rate to 100 Mbps, known as Fast Ethernet
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13-3 FAST ETHERNET13-3 FAST ETHERNET
The designers of the Fast Ethernet made it compatible with the Standard Ethernet.
The MAC sublayer was left unchanged.
But the features of the Standard Ethernet that depend on the transmission rate, had to be changed.
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13.3.1 Access Method13.3.1 Access Method
Proper operation of the CSMA/CD depends on the ●transmission rate, ●the minimum size of the frame, and ●the maximum network length.
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13.3.1 Access Method13.3.1 Access Method
For backward compatibility, Fast Ethernet must detect the collision 10 times sooner (compared to standard ethernet)
This means the maximum length of the network should be 10 times shorter (the propagation speed does not change).
2500m becomes 250m (in practice the limit is 100m per segment)
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13.3.2 Physical Layer13.3.2 Physical Layer
To be able to handle a 100 Mbps data rate, several changes need to be made at the physical layer.
13.47
Figure 13.16: Encoding for fast Ethernet
Table 13.2: Summary of Fast Ethernet implementations
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13.49
13-4 GIGABIT ETHERNET13-4 GIGABIT ETHERNET
The Gigabit Ethernet Protocol (1000 Mbps) is the Standard 802.3z.
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13-4 GIGABIT ETHERNET13-4 GIGABIT ETHERNET
The goals of Gigabit Ethernet were to ●upgrade the data rate to 1 Gbps, and ●keep the address format, ●the frame format, and ●the maximum and minimum frame length the same.
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13-4 GIGABIT ETHERNET13-4 GIGABIT ETHERNET
●The goals of Gigabit Ethernet requires a star topology.
(the bus topology is not allowed)
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13.4.1 MAC Sublayer13.4.1 MAC Sublayer
Gigabit Ethernet has two distinctive approaches for medium access: half-duplex and full-duplex.
Almost all implementations of Gigabit Ethernet follow the full-duplex approach.
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13.4.2 Physical Layer13.4.2 Physical Layer
The physical layer in Gigabit Ethernet is more complicated than that in Standard or Fast Ethernet. We briefly discuss some features of this layer.
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Figure 13.17: Encoding in Gigabit Ethernet
Table 13.3: Summary of Gigabit Ethernet implementations
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13.56
13-5 10-GIGABIT EHTERNET13-5 10-GIGABIT EHTERNET
In recent years, there has been another look into the Ethernet for use in metropolitan areas. The idea is to extend the technology, the data rate, and the coverage distance so that the Ethernet can be used as LAN and MAN (metropolitan area network). The IEEE committee created 10 Gigabit Ethernet and called it Standard 802.3ae.
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13.5.1 Implementation13.5.1 Implementation
10-Gigabit Ethernet operates only in full-duplex mode.
It can be implemented with copper wire (cat-6a or higher) but is limited to 100m.
Fiber segments can be up to 40km.
Table 13.4: Summary of 10-Gigabit Ethernet implementations
13.58